1. Field
The subject matter disclosed herein relates to mobile electronic devices, and, more particularly, to methods, apparatuses, and articles of manufacture that may be used to acquire differing wireless positioning reference signals transmitted during differing occasions.
2. Information
The Global Positioning System (GPS) and other like satellite positioning systems (SPS) have enabled navigation services for mobile devices in many types of outdoor environments. In addition to, or in place of, SPS-based approaches for obtaining accurate estimations of position, a mobile device may employ positioning approaches that may involve acquisition of signals transmitted by terrestrial transmitters, such as cellular base station transmitters, which may be positioned at known locations. Such approaches may include, for example, observed time difference of arrival (OTDOA) and/or other procedures, such as advanced forward link trilateration (AFLT).
For example, if an OTDOA technique is utilized, a cellular communications network may estimate a position of a mobile device responsive to a mobile device reporting differences in observed time of arrival of signals transmitted from cellular base stations. However, if one or more signals received at a mobile device are distorted and/or accompanied by excessive interference, the mobile device may be unable to acquire the signal and, consequently, be unable to accurately determine time of arrival of signals. Consequently, a mobile device may report inaccurate values of observed time differences among acquired signals. Such inaccuracies in time of arrival, if processed by a cooperating cellular network, may give rise to considerable errors in computing an estimated location of the mobile device.
Errors in estimating a position of a mobile device, which may be brought about by measurement of distorted and/or noisy signals transmitted from cellular base stations, may be particularly troubling in many scenarios. For example, in an emergency services setting, in which an enhanced 911 system (e.g., E-911) may be used to locate one or more mobile device users who may need medical assistance, paramedics may spend an inordinate period of time attempting to locate an injured mobile device user on a busy highway. In other instances, position estimation errors may bring about reduced accuracy of turn-by-turn directions provided by a navigation or route planning application. Such misdirection can be a source of frustration among many types of mobile device users who rely on a capability for accurate position estimation.